Electric incandescent lamp



Oct. 25, 1938. E. B. PINKL:E

ELECTRIC I NCANDESCENT LAMP Filed Aug. 24, 1937 Figl.

lrwverwtor: Emma B Pinkie,

' He Aotorney.

Patented Oct. 25, 1938 PATENT OFFICE ELECTRIC INCANDESCENT LAMP Emma B.Pinkie, East Cleveland, Ohio, assignor to General Electric Company, acorporation of New York Application August 24,

' 3' Claims.

My invention relates to electric incandescent lamps and moreparticularly to'high wattage lamps. Still more particularly, myinvention relates to an improved joint between the lamp filament and itsleading-in conductors.

Heretofore, in high wattage lamps of the type wherein the filamentcomprises a number of coiled segments arranged substantially parallel toeach other, it has been the practice to wind the filament with extracoiled segments at the ends thereof which were short-circuited byinserting a mandrel therein and then welded to-- \gether with theirmandrels to the leading-in conductors. Such a joint has the disadvantagethat the mandrel may not make a positive contact with some of the turnsof the end segment so that those turns are heated by the current passingthrough the lamp thereby increasing the efiective length of the filamentover its designed length. Moreover, the welding operation tends to makethe tungsten filament brittle so that it is liable to break off if thelamp is jarred.

One of the objects ofmy invention is to provide an improved form ofjoint between the filament and the leading-in conductors. Another objectis to provide a joint in which the end segments of the filament areeffectively short-circuited. Still another object is to greatly increasethe strength of the joint and to provide a good mechanical andelectrical connection of the filament to the leading-in conductors.

Further objects and advantages of my invention will appear fromthefollowing description of a species thereof and from the drawing in whichFig. 1 is an elevation of one form of incandescent lamp embodying myinvention; Fig. 2 is an elevation, partly in section and on an enlargedscale, of a portion of the filament joint; and Fig. 3 is a section alongthe line 3-3 of Fig. 1 showing a portion of the filament and itssupporting structure.

Referring to the drawing, the lamp shown therein comprises a glass bulbl0 having a base construction of the type shown and claimed in UnitedStates Patents Nos. 1,967,852 and 2,069,- 638, D. K. Wright, andconsisting of a pressed glass cup portion ll having tubular bosses l2-l2thereon to which are sealed metal thimbles l3-|3 which serve formounting the lamp and for conducting current thereto. Channel-shapedmetal supports or leading-in conductors l4l4 are secured at their endswithin the thimbles |3-l3 and extend into the bulb Ill. The leads l4-I4may be made of nickel-plated steel and may be provided with rod or wire,end portions 1937, Serial No. 160,621 (Cl. 176-38) l5-l 5, of molybdenumfor example, welded thereto and extending on opposite sides of thetungsten filament It. The leads are held in rigid spaced relationship bycross-bars ||-l8 of insulating material, preferably a ceramic materialsuch as siliminite. The cross-bar I1 is secured to the leads M-M byshort lengths of wire l9l9 threaded through holes in the ends of thecrossbar and in the leads and welded to the leads. The cross-bar I8. issecured to the ends of the 10 lead extensions I5-I5 by similar wires20-40 welded to said extensions.

The filament l6 illustrated in the drawing is' of the biplane typecomprising a plurality of parallel coiled segments. joined by upper and15 lower uncoiled or bight portions 2| and 22 respectively, thealternate segments in this case being located in separate planes so thatone-half of said segments are in one plane and the other half of saidsegments are disposed behind said 20 first half in another plane. "Thefilament is supported at the top by support wires 23 having hooked lowerends engaging the upper bights 2| and secured at their upper ends to thecross-bar H. The lower bights 22 are rigidly secured, pref- 25 erably bywelding, to the upper ends of anchor wires 24, the lower ends of whichare rigidly secured to an insulating bridge member 25 which may be madeof zircon. The said anchors may be embedded in the bridge25. Each of'gulde 30 wires 2626 has one end secured to the bridge 25 and the otherend loosely coiled around a lead extension l5 so as to be freelyslidable thereon so that the filament I6 is free to expand in alongitudinal direction and the bridge 25 moves therewith but isprevented from rotatingby the said guide wires 26 thereby preventing thesegments of the filament from twisting. The bridge 25 is further guidedby a wire 21 secured thereto and extending through a hole in thecross-bar l8.

Each end of the filament I6 is wound with a coiled segment 28 (Fig. 2)over which is screwed a coil 29, preferably of tungsten wire, of substantially the same length as the said segment 28 to short-circuit the saidsegment. The coil 29 is 45 of the same pitch as the segment 28 andpreferably is made of a wire of slightly smaller diameter. A conductivesupport or mandrel 30 extends through the segment 28 which is securelyheld between a hooked end 3| of the mandrel 50 and the cross-bar H, thesaid mandrel extending through a holein'said cross-bar and beingsecured, preferably by welding, to the lead It. The hook 3| on the endof mandrel 30 may be omitted if desired sincethe segment 28 grips themandrel quite tightly. Such a joint adds greatly to the having a coiledend portion, a coil screwed over strength of the lamp, provides a goodmechanical said coiled end portion of said filament and shortandelectrical connection of the filament to the circuiting the turnsthereof, and a conductive leads and assures the short-circuiting of all01' mandrel in contact with and extending through the turns in thefilament end segments 28. said coiled end portion or said filament and 5What I claim as new and desire to secure by r h Said r sr $0 One d l s.aid Letters Patent of the United state is; filament end portion and thecoil thereon being 1. In an incandescent lamp, the combination secure yd e w e sa d c ssa and the end of a conductive lead, a filament having acoiled of sa d mand e end portion, a coil screwed over said coiled endIn n incandescent p. the com ination 10 portion of said filament andshort-clrcuiting the f a filament, aconductive support f r S pp y nturns thereof, and a conductive mandrel in concurrent to said filament,said filament having a tact with and extending through said coiled endcoiled end portion surrounding and making elecportion of said filamentand secured to said contrical contact with said support and a coilscrewed ductive lead at a point removed fromsaid coils. over said coiledend portion of said filament and 15 2. In an incandescent lamp, thecombination short-circuiting the turns thereoi. 01 a pair of spacedconductive leads, an insulating cross-bar extending between said leads,a filament EMMA B. PINKLE.

